Wide-angle objective of large back-focal length



May 19, 1970 vv. 'Vul-Ibn; WIDE-ANGLE OBJECTIVE OF LARGE BACK-FOCAL LENGTH Filed Oct. 13, 1967 3 Sheets-Sheet 1 F/gJ f7 r9 r11-H3 rl5 ra flo n2! r1.4 ne

d8 ZI d2 d5 d9 dll dl3 d75 Walter Wlche Inventor.

Attorney May 19, 1970 w. WLTCHE 3,512,874

WIDE-ANGLE OBJECTIVE OF LARGE BACK-FOCAL LENGTH Filed 061'.. 13. 1967 3 Sheets-Sheet 2 6 ds' dn d7 d8 d70 l Il l L4 e5, Tgg L w,

Walter Wlche Inventor.

By @.B'oss Attorney May 19, 1970 w. wLTcHE 3,512,874

WIDE-ANGLE OBJECTIVE OF LARGE BACK-FOCAL LENGTH Filed Oct. l5. 1967 3 Sheets-Sheet 3 Figi' I s" C112". du" als d5" a7" da" dro" dn" als" d15"d17 L3 La" L5" L6" L7" La" L9" L10 Il Il ll Il n Il 1I 1V l? JZZ lZZZ im 'Bil CII DI! B Y A 93" Attorney United States Patent Office U.S. Cl. 350-214 3 Claims ABSTRACT F THE DISCLOSURE Optical objective composed of 8 lens members, the 2nd, 3rd and 6th member being negatively refracting, the 4th and 5th members each having an axial width greater than that of any other member, the.lst, 2nd, 3rd and 7th members being meniscus-shaped and concave toward a diaphragm space separating the 5th and 6th members, the 6th member being biconcave whereas the 8th member is either biconvex or planoconvex.

My present invention relates to a wide-angle optical objective for photographic or cinematographic cameras.

In my copending application Ser. No. 619,115, led Feb. 20, 1967, I have disclosed an objective of this general type with a dispersive front group consisting of two negatively refracting menisci and a collective rear group consisting of two positive members forwardly of a diaphragm space, a biconcave lens beyond that diaphragm y space and a biconvex rear lens following the biconcave lens. The system specifically described in that prior application has a relative aperture of 1:4, a back-focal length of approximately 1.3 times the overall focal length, and a field angle of 75. v

The general object of my present invention is to provide an improved system of the type referred to which, with an aperture ratio of 1:4 or better, has a considerably increased back-focal length and a field angle upwardly of 80.

This object is realized, in accordance with my present invention, by the provision of a front lens in the form of a positive, meniscus ahead of the two negative menisci and by the interposition of another positive meniscus between the biconcave lens and the following rear lens, all the menisci of the system turning their concave sides toward the diaphragm space; in addition, the two positive lens members immediately preceding the diaphragm space are given an axial thickness greater than that of any other lens in the system, with corresponding reduction of the preceding air space which in my prior system amounts to almost of the overall focal length.

The present objective system is thus composed of eight air-spaced lens members whose individual focal lengths have been designated hereinafter by f1 to fvm. I have found that, for -best results in terms of suppression of aberrations, these individual focal lengths should be related to the overall focal lengths f substantially as follows:

3,-5121874 Patented May 19, 1970 In somewhat more specific terms, with the individual focal length fm of the third front-side meniscus taken as a reference parameter, the preferred relationship between the absolute value of these individual focal lengths may be expressed as follows:

Of particular significance for the suppression of field curvature is the dimensioning of the axial thicknesses of the positively refracting fourth and fth lens members immediately preceding the diaphragm space. According to another feature of my invention, these axial thicknesses should exceed not only the individual axial thickness of i any other lens member but also the combined axial thicknesses of the first and second lens members as well as the combined axial thicknesses of the three last (image-side) lens members positioned beyond the diaphragm space. The axial thicknesses dw and dv of these fourth and fifth members preferably range between substantially 2.5 and 5 times the absolute value of fm. The focal length fw of the positive fourth member preferably exceeds, in absolute terms, that of any other lens member.

In the accompanying drawing, FIGS. 1, 2 and 3 diagrammatically illustrate three representative embodiments of an objective according to the invention.

The objective shown in FIG. l consists of eight singlets I to VIII combined into foul distinct components A, B, C and D. Component A consists of a positive meniscus L1 with radii r1, r2 and thickness d1, a negative meniscus L2 with radii r3, r4 and thickness d3 and another negative meniscus L3 with radii rS, r6 and thickness d5; the intervening air spaces have been designated d2 and d4. The second component B, separated from component A by an air space d6, is a planoconvex lens L4 with radii r7, f8 and thickness d7. The third component C; spaced from component B by a distance d8, is a biconcave lens L5 with radii r9, 1310 and thickness d9. Following a diaphragm space d10, there are three more lenses constituting the fourth component D, i.e. a biconcave lens L6 with radii r11, :'12 and thickness d11, a positive meniscus L7 with radii r13, r14 and thickness d13, and a biconvex rear lens L8 with radii :'15, w16 and thickness d15, the air spaces separating these three lenses having been designated d12 and d14.

The following Table 1 lists representative numerical values for the radii r1 to :'16 and the thicknesses and separations d1 to d15 of lens members I to VIII, based on an overall focal length f of linear units (e.g. mm.), together with their refractive indices n,a and Abbe numbers v, given for a spectral wavelength )\=546.l ma, as well as the refractive power An/r for each of the lens surfaces in absolute terms, to be compared with an overall power of 1/f=0.01. This system has an aperture ratio of 112.8,

a back-focal length of 147.38 and a field angle of 80, suitable for a frame sizeof 24 X 36 mm2 when f=25 mm.

TABLE 1 Thicknesses Lens Radii and n. v An/r separations r1= +242. 39 +0. 002570 L1 d1 19. 52 1. 62287 d2=0. 39 Air space r3= +146. 20 +0. 004260 L2 d3=9. 76 1. 62287 60. 06

d4=19. 52 Air space r5=+115. 32 +0. 005401 L3 d5=5. 86 1. 62287 60. 06

d6=21. 47 Air space r7=e 0. 000000 L4 d7=35. 13 1. 69416 30. 93

d8=0. 78 Air space r9=+96 39 +0. 006076 L5 d9=40. 99 1. 58564 46. 22

d10 14. 83 Diaphragm space r11=77. 45 0.009834 L6 d11=4. 68 1. 76167 27. 34

d12=5. 47 Air spa ce r13= 244. 14 0. 002551 L7 d13=11. 71 1. 62287 60. 06

d14=0. 39 Air space r15= +585.88 +0. 001063 L8 d15=11. 71 .1. 62287 60. 06

FIG. 2 shows a similar system whose four components A', B', C and D consist again of eight lens members I' to VIII constituted in this case by nine individual lenses L1 to L9; their radii have been designated r1 to r17 while their thicknesses and separations are indicated at d1 to d16.

In contradistinction of the system to FIG. 1, the objective of FIG. 2 includes a doublet L4', L5 in the position of thefourth lens member IV. The cemented surface r8' of this doublet is negatively refracting and forwardly con- Vex', in addition to reducing chromatic aberrations, the use of this doublet further improves the quality of the projected image as expressed in an increased field angle. Representative numerical values for the parameters of FIG. 2 are given in the following Table 2. This system has a relatlve aperture of 1 :4, a back-focal length of 174.79 and a field angle of 90.

TABLE 2 Thicknesses Lens Radil and n., v An/r separations r1'= +290.88 +0. 001962 L1f.....- d1=27.91 1. 57086 d2=0.47 Air space r3=+139.49 +0. 004465 L2' d3 10.23 1. 62287 60. 06

d4=27.01 Air space f5 +148.09 +0. 004464 L3 d5=8.37 1. 66104 d6=25.58 .Air space r7=0o 0. 000000 L4' 17' =27.91 1. 62287 60. 06

r8'= +8219 0. 000875 L5 d8 =25.12 1. 55098 45. 61

d9=0.93 Air space r10= +109.35 +0. 005039 L6 d10 =46.51 1, 55098 45. 61

d11=13.95 Diaphragm space r12= 73.30 0.010191 L7' d12'=5.12 1. 74703 27. 82

d13=3.26 Air space r14= 318.65 0.001955 L8 (114 9,30 1. 62287 60. 06

d15'=0.47 Air space r16=00 0. 000000 L9' l10= 9.30 1.62287 60. 06

The system of FIG. 3 differs from that of FIG. 2 by the presence of a further doublet in the position of the fifth lens member V"; its eight lens members I" to VIII, constituting the four components A", B", C" and D", thus consist of 10 individual lenses Ll to L10 whose radii and thicknesses and separations have been respectively designated r1" to r18 and d1 to d17.

The cemented surface r11 of double V is rearwardly convex and positively refracting, as are its two constituent lenses L6" and L7. The presence of this second cemented surface is particularly effective in suppressing higher-order entrance-pupil and asymmetrical aberrations.

Representative numerical values for the parameters of the system of FIG. 3 are listed in the following Table 3. This objective has the same aperture ratio and eld angle as that of Table 2 and a back-focal length of 173.92; both systems are suitable for a frame size of 24 X 36 mm." with f=21 mm.

TABLE 3 Thicknesses Lens Radii and n. v An/r Separations r1= +285.31 +0. 001848 L1l d1 =27.68 1. 52736 64. 31

d2=0.46 Air space 13: +138.37 +0. 004501 L2" d3"=10.15 1. 62287 60.06

d4"=27.68 Air space f5 +146.90 +0. 004500 L3..... d5"=8.30 1. 66104 57.08

r6 +4835 0. 013672 d0 =25.38 Air space T7 =0 0. 000000 L4 d7=32.30 1. 62287 60. 06

r8= +8152 0.001074 L5". d8 =20.30 1. 53530 45. 67 r9=-274.84 +0. 001948 d9=0.92 Air space T10 +112.07 +0. 005453 L6.. d10=18.54 1. 61114 45. 92

r11 =-346.45 +0. 000222 L7.. d11=26.76 1. 53430 48. 66

d12=13.84 Diaphragm space r13= 72.25 0.010328 L8" d13"=5.08 1.74618 27. 97

d14= 3.23 Air sp ace r15= +259.71 0. 002398 L9. d15"=9.23 1. 62287 60.06

d16=0.46 Air space r17=0 0.000000 L10 d17=9.23 1. 59142 61.03

The numerical values of the foregoing tables are to be understood as valid within tolerance limits of substantially il0% for the radii, thicknesses and separations, the surface powers and the Abbe numbers, and of substantially :0.02 for the refractive indices. In view of these tolerances, the last three digits in the ne column and the decimals in the other columns are only of minor significance.

It will be observed that the two last components C, C', C" and D, D', D" of my improved objective do not exhibit any dispersive internal surfaces which in prior-art objectives are responsible for appreciable spherical aberrations and chromatic divergences of the entrance-pupil (Gaussian) aberration.

The following Table 4 summarizes the individual focal lengths of the eight lens members of each of the three aforedescribed objective systems.

TAB LE 4 Table 1 Table 2 Table 3 It will thus be seen that each of the three systems specifically described hereinabove satisfies the aforestated relationships of the individual focal lengths with one another and with the axial thicknesses of the two intermediate positive lens members.

I claim:

1. An eight-member optical objective consisting of a positive first singlet L1, a negative second singlet L2, a negative third singlet L3, a positive fourth singlet L4, a positive fifth singlet L5, a negative sixth singlet L6, a positive seventh singlet L7 and a positive eighth singlet L8, the numerical values of the radii r1 to r16 and the thicknesses and separations d1 to d15 of said singlets L1 to L8, based upon an overall focal length of numerical value 100, their refractive indices ne and their Abbe numbers v, for a wavelength \=546.l mit, being substantially as given in the following table:

Thcknesses Lens Radii and ne v Separat ions r1= +242.39 L1 (11:10.52 1. 62 60. 0G

d2= 0. 39 Air space f8 -i- 146.20 L2 d3=9.76 1.62 60. 06 r4= +7105 d4=19.52 Air space f5 115.32 L3 d5 =5.86 1. 62 60.06

d6=21.47 Air space r7=0 L4 d7=35.13 1. 69 30. 92

d8= 0. 78 Air space r9 +9639 L5 d9=40. 99 1. 59 46. 22

d10=14.83 Diaphragm space r11= 77.45 L6 d1l=4.68 1.76 27.34

r12= +1es.s8 n

d12=5.47 Air space r13=-244.14 L7 d13=1l.71 1.62 60.06

dl4=0.39 Air space r15= +585. 88 L8 d15=11. 71 1.62 60.06

2. An eight-member optical objective consisting of a positive first lens member, a negative second lens member, a negative third lens member, a positive fourth lens member, a positive fifth lens member, a negative sixth lens member, a positive seventh lens member and a positive eighth lens member, said fourth lens member being a doublet consisting of a negative first lens and a positive second lens separated by a negatively refracting cemented surface, the remaining lens members being all singlets, the numerical values of the radii r1 to r17 and the thicknesses and separations d1' to d16' of said singlets L1 to L3', L6 to L9', said first lens L4 and said second lens L5', based upon an overall focal length of numerical value 100, their refracted indices ne and their Abbe numbers v, for a wavelength )\=546.l mp, being substantially as given in the following table:

Thicknesses Lens Radn and n, v

separations r1= +290.88 L1 2l F91 16 d1'=27.91 1. 57 63.01

3l +139 49 d2=0.47 Air space T L2. 4l +72 60 d3=10.23 1. 62 60. 06

5 +148 09 d4=27.91 Air space T L3 d5=8.37 1.66 57.08

7l d6=25.58 Air space T :OO L4 8l +82 19 d7=27.91 1. 62 60. 06

T L5 9, 277 07 d8=25.12 1. 55 f 45. 61

lo, +109 35 d9=0.93 Air space r L6' d10'=46.51 1. 55 45. 61

d11= 13.95 Diaphragm space r12=73.30

d13=3.26 Air space r14=318.65 L8 15, *68 14 d14=9.30 1. 62 60.06

16 d15=0.47 Air space l =OO L9 17, 105 26 d16=9.30 1. 62 60.06

3. An eight-member optical objective consisting of a positive first lens member, a negative second lens member, a negative third lens member, a positive fourth lens member, a positive fifth lens member, a negative sixth lens member, a positive seventh lens member and a positive eighth lens member, said fourth lens member being a doublet composed of a negative first lens and a positive second lens separated by a negatively refracting forwardly convex cemented surface, said fifth lens member being a doublet composed of a positive third lens and a positive fourth lens separated by a positively refracting rearwardly convex cemented surface, the other of said lens members being all singlets, the numerical values of the radii r1 t0 1'18 and the thicknesses and separations d1 to d17l of said singlets L1 to L3, L8" to L10, said first lens L4, said second lens L5", said third lens L6 and said fourth lens L7", based upon an overall focal length of numerical value 100, their refracted indices ne and their Abbe numbers v, for a wavelength \=546.1 mit, being substantially as given in the following table:

References Cited UNITED STATES PATENTS 8/1936 Sonnefeld 350-214 4/1951 Bertele 350-216 FOREIGN PATENTS 3/1966 Germany. 6/1964 France.

10 DAVID SCHONBERG, Primary Examiner P. A. SACHER, Assistant Examiner 

